CN110678163A

CN110678163A - Nanoemulsion comprising sulfoalkyl esters and/or amides of fatty acids in aqueous phase

Info

Publication number: CN110678163A
Application number: CN201880025863.0A
Authority: CN
Inventors: 权聪玲; D·J·兰; B·D·卡斯巴罗
Original assignee: Unilever Nederland BV
Current assignee: Unilever IP Holdings BV
Priority date: 2017-04-20
Filing date: 2018-03-29
Publication date: 2020-01-10
Anticipated expiration: 2038-03-29
Also published as: CA3060324A1; JP7198552B2; BR112019019394B1; BR112019019394A2; EA201991931A1; US20210128421A1; ZA201906214B; JP2020517582A; US11234908B2; WO2018192761A1; EP3612150A1; MX2019012327A; EP3612150B1; CN110678163B

Abstract

The present invention relates to novel oil-in-water pumpable nanoemulsions. The oily phase comprises an oil selected from triglyceride oils and/or petrolatum and C₈‑C₁₈A fatty acid; and the aqueous phase contains sulfoalkyl esters and/or amides of fatty acids as emulsifiers.

Description

Nanoemulsion comprising sulfoalkyl esters and/or amides of fatty acids in aqueous phase

Technical Field

The present invention relates to novel oil-in-water (o/w) nanoemulsions. The nanoemulsion comprises (1) a mixture of (a) a triglyceride oil and/or a petrolatum and (C)₈-C₁₈An internal oil phase of fatty acids; (2) an external aqueous phase comprising an anionic surfactant which is a sulfoalkyl ester and/or amide of a fatty acid.

Background

The present invention relates to providing nanoemulsions comprising triglyceride oils and petrolatum (benefit agent delivered from the nanoemulsions) in small droplets (e.g., 400nm or less); these are considered to be more aesthetically pleasing than compositions that deliver benefit agents in the form of larger oil droplets. The nanoemulsion further provides a high deposition of triglyceride oils and/or petrolatum when incorporated into a personal cleansing composition. Further, surprisingly, excellent foaming properties of personal cleansing compositions were found when these benefit agents were present in the form of droplets of 400nm or less. Generally, triglyceride oils and petrolatum benefit agents tend to suppress foaming rate and volume when in the form of droplets of several microns.

The applicant has previously filed applications in which the primary emulsifier (in the aqueous phase) is an N-acyl derivative of a mono-or dicarboxylic amino acid. Both can be provided in liquid solution form, with concentrations ranging from 20% to 35% at ambient temperature. The N-acyl derivatives of both dicarboxylic acid and monocarboxylic amino acid surfactants are exceptionally mild and very expensive.

Sulfoalkyl esters and/or amides of fatty acids are other types of mild surfactants that are generally more economically produced than more expensive surfactants (e.g., the N-acyl derivatives of mono-or dicarboxylic amino acids described above). An example of a sulfoalkyl ester of a fatty acid is sodium acyl isethionate, a well-known mild anionic surfactant, which has been widely used in cosmetic compositions, for example

Bath BarsOf these, sodium acyl isethionate is the most abundant component. Sodium acyl isethionates have also been formulated as liquid cleansers, such as body washes, to replace harsh surfactants, such as sodium lauryl ether sulfate. The sulfoalkyl amide of the most widely used fatty acid, sodium methyl alkyl taurate, is desirably mild and provides excellent lather.

The use of sulfoalkyl esters and/or amides of fatty acids as primary emulsifiers in the aqueous phase to produce nanoemulsions is functionally and economically attractive, but very challenging. The oil droplets of nanoemulsions made with sodium acyl isethionate as the only emulsifier tend to be larger, e.g., greater than 400 nanometers (nm) after one pass through a high pressure homogenizer at 5000 pounds per square inch (psi) pressure. Furthermore, due to the poor solubility of sodium acyl isethionates in water, nanoemulsions made from sodium acyl isethionates tend to solidify at ambient temperatures and are therefore difficult to pump. The solubility of sodium cocoyl isethionate in water at 25 ℃ is only 0.01 wt% (j.cosmet.sci.,54, 559-one 568, 11/12 months 2003).

The solubility of sodium methyl cocoyl taurate in water at 25 ℃ is about 1% by weight. It may be provided as a paste with 20% -35% active. When sodium methyl acyl taurate was used as the sole emulsifier for the preparation of the petrolatum nanoemulsion, the oil droplets were greater than 600nm after one pass through the high pressure homogenizer at 5000psi pressure, although no solidification occurred at ambient temperature.

Applicants have now found that the use of fatty acids (in the oil phase of the nanoemulsion) as co-emulsifiers provides some unexpected advantages. First, it allows the use of less expensive, poorly soluble anionic mild surfactants (e.g., sodium acyl isethionate) in the preparation of pumpable nanoemulsions at ambient temperature. Also, nanoemulsions with much smaller droplet sizes can be prepared more efficiently (e.g., lower process pressures and/or fewer passes through the homogenizer). Furthermore, the use of fatty acid co-emulsifiers allowed the formation of small volume average droplets (100-400nm) of our invention. In the absence of fatty acid emulsifiers, the volume average of the petrolatum droplets (using isethionate or taurate surfactants as emulsifiers) is well above 400 nm.

Another advantage of using fatty acids as co-emulsifiers is that more economical grades of sulfoalkyl esters and/or amides of fatty acids can be used to further reduce the cost of the nanoemulsion. Sulfoalkyl esters and amides of fatty acids by reacting fatty acids (e.g. C)₁₀-C₁₈Fatty acids) with, for example, sodium isethionate (HOCH)₂CH₂SO₃ ^-Na⁺) And sodium methyl taurate (NH)₂CH₂CH₂SO₃ ^-Na⁺) Reacted to manufacture commercially. To obtain high yields, the fatty acids are usually in excess to increase the yield and reduce side reactions (Anionic Surfactants Part 2, Surfactant Science Series, Vol.7, p.458-461). Finally, the fatty acids are removed by vacuum distillation, which increases cycle time and energy consumption, thus increasing production costs. The undistilled mixture can be well used to efficiently prepare pumpable nanoemulsions of the desired oil droplets.

In particular, the co-emulsifier, which is the subject of the present invention, allows the preparation of particularly small petrolatum droplets (e.g. 300nm and below, preferably 250nm and below, more preferably 200nm and below) in an efficient manner and further allows the use of poorly soluble anionic mild surfactants to prepare nanoemulsions that are pumpable at ambient temperatures.

Skin moisturizing oils (including the triglyceride oils and petrolatum benefit agents mentioned above) are typically delivered from personal cleansing compositions (e.g., shower gels, facial and hand cleansers designed to cleanse and moisturize the skin) in the form of large oil droplets (e.g., 50 to 200 microns or more).

For example, U.S. patent nos. 5,584,293 and 6,066,608 to Glenn, jr. disclose a moisturizing liquid personal cleansing emulsion having at least 10% lipophilic skin moisturizer droplets greater than 200 microns in diameter.

U.S. patent No.8,772,212 to Restrepo et al discloses an isotropic cleaning composition containing a high level of petrolatum; more than 50 volume% of the petrolatum particles have a diameter greater than 50, 100, 150 or 200 microns.

Compositions containing large oil droplets need to be well structured so that they can suspend the large droplets (using, for example, stabilizers). For example, U.S. Pat. Nos. 5,854,293 and 6,066,608 use a stabilizing agent selected from crystalline, hydroxyl-containing stabilizers, polymeric thickeners, C₁₀To C₁₈Diesters, amorphous silica or montmorillonite clay. Special mixing methods are usually required to prepare such compositions. For example, the composition must be prepared at low shear to prevent the reduction in oil droplet size (see U.S. patent No.8,772,212). Although they provide enhanced benefit agent delivery, these products are generally considered less aesthetically appealing to consumers due to the presence of large oil droplets.

Another method of enhancing delivery of benefit agents (e.g., silicones) to the skin, for example, is through the use of cationic hydrophilic polymers such as, for example, hydroxypropyl trimethylammonium derivatives of guar gum, to enhance delivery of benefit agents (e.g., silicones) to the skin

C-13-S is sold under the name Helliwell (see U.S. Pat. No.5,500,152 to Helliwell). In this reference, the silicone oil is a preformed emulsion having an oil droplet size of 0.1 to 1 micron (μm) and an average particle size of 0.4 μm (no mention is made of whether this refers to the number average or volume average diameter of the droplets). Such products tend to be smooth and aesthetically appealing. However, nourishing vegetable oils (triglyceride oils) and highly occlusive skin protectants, such as petrolatum, are often preferred moisturizers from cleansing compositions.

One challenge facing moisturizing oil-rich cleaning compositions is that large amounts of oil tend to reduce foaming speed and volume.

It would therefore be desirable to prepare personal cleansing compositions consisting of triglyceride oils and/or petrolatum nanoemulsions that are aesthetically appealing, have a high deposition of these moisturizing oils, and which maintain high foaming properties.

In the present invention, applicants provide novel o/w nanoemulsions for delivering triglyceride oils and petrolatum as small (100-. Furthermore, unexpectedly, high foam performance was maintained.

As mentioned above, in the co-pending application, the applicant claims an o/w nanoemulsion comprising a salt of an N-acyl derivative of a mono-or dicarboxylic acid amino acid, which can be provided in the form of a liquid solution at ambient temperature, at a concentration of 20-35%. In the present application, fatty acids are used as co-emulsifiers and, unexpectedly, the applicants have found that the use of poorly soluble anionic mild surfactants can produce pumpable nanoemulsions at ambient temperatures. Sulfoalkyl esters and amides of fatty acids are well known mild anionic surfactants and have wide application in cosmetic compositions. They are cheaper than amino acid based surfactants in previous applications.

The nanoemulsion of the present invention comprises: (1) an oil phase comprising droplets of a benefit agent selected from triglyceride oils, petrolatum and mixtures thereof, and C₈-C₁₈A fatty acid co-emulsifier; and (2) an aqueous phase comprising one or more surfactants (primary emulsifiers) which are sulfoalkyl esters of fatty acids or sulfoalkylamides of fatty acids, or mixtures of these.

The sulfoalkyl ester of a particular fatty acid or sulfoalkyl amide of a fatty acid typically comprises 70% or more, preferably 75% or more, more preferably 80% or more of all surfactants present in the aqueous phase of the nanoemulsion composition. The sulfoalkyl ester of a fatty acid or sulfoalkyl amide of a fatty acid is present in a greater amount than any other surfactant present in the aqueous phase. Additional ionic surfactants may be present in the aqueous phase which help to increase the solubility of sodium acyl isethionate or sodium methyl acyl taurate. Such surfactants, known as solubilizers, typically consist of head groups similar to or larger and more complex than those of sodium acyl isethionate or sodium methyl acyl taurate. Anionic and amphoteric surfactants can achieve this. In the class of anionic surfactants, these are (but are not limited to): sodium (or ammonium) dialkyl sulfosuccinates, disodium (or diammonium) alkyl ether sulfosuccinates, disodium (or diammonium) acyl glutamates, sodium (or ammonium) acyl lactylates, and sodium acyl sarcosinates. Sodium methylacyl taurate and sodium acyl isethionate share similar head groups and thus aid in dissolution with each other. Within the amphoteric class, there are alkylamidopropyl hydroxysulfosulfonates, sodium (or ammonium) alkylamphoacetates, disodium (or diammonium) alkylamphopropionates, sodium (or ammonium) alkylamidodipropionates, disodium (or diammonium) alkylamidopropyl betaines, and sodium alkylamidopropyl sulfonates. The solubilizer surfactant typically comprises 30% or less, preferably 25% or less, more preferably 20% or less of all surfactants present in the aqueous phase of the nanoemulsion composition.

In U.S. patent No.6,541,018 to simonet et al, the internal phase oil is predominantly a lower molecular weight ester oil (MW less than 400). The lower MW ester oil affects the viscosity and foam of the cleaning composition. The triglycerides and petrolatum of our invention (having a melting point of 30 to 60 ℃) help maintain good viscosity and foam.

Note that the nanoemulsions disclosed in both US8,834,903 and US6,541,018 of simonet et al have an internal phase, where the concentration of oil is no higher than 40% of the emulsion. Although the concentration of the oil of the present invention may range from 40 to 75 wt% of the total nanoemulsion, the preferred range is 41 to 70 wt%, preferably 50 to 65 wt%. A higher internal phase is beneficial not only because it consumes less energy to make a nanoemulsion of smaller droplets, but also improves the yield of nano-oil droplets.

U.S. patent No. 2003/0012759A1 to Bowen-weaver teaches the preparation of nanoemulsions at about 10,000 and 20,000psi and multiple passes using a high pressure apparatus ([0021], page 3). In example 1 an emulsifier system consisting of anionic surfactant (sodium stearoylglutamate), nonionic surfactant (glyceryl stearate/PEG-100 stearate) and stearic acid is disclosed. The fatty acid was used in the oil phase together with glyceryl stearate/PEG-100 stearate as a co-emulsifier. There is no mention of the key to the use of anionic surfactants such as sodium acyl isethionate or sodium methyl acyl taurate in combination with fatty acids as emulsifiers to improve the production efficiency and ambient temperature pumpability of the nanoemulsion. In our application, the emulsifier system used to prepare the nanoemulsion does not contain non-ionic emulsifiers such as glyceryl stearate and PEG-100 stearate. It has been found that the combination of anionic surfactant and fatty acid unexpectedly reduces the petrolatum nanoemulsion droplet size to below 400nm at only one pass and at 5,000psi or less in the absence of any other nonionic surfactant. This process efficiency is totally unpredictable based on the use of fatty acids.

WO02/080864a1 discloses oil-in-water nanoemulsions comprising as its primary emulsifier a surfactant ternary system comprising a cation, an anion and a bridging surfactant (line 2, lines 16-17). The nanoemulsion was prepared by passing through a high pressure microfluidizer at least twice at 10,000-20,000psi (page 3, lines 14-17). Taurates and isethionates are two of the preferred anionic surfactants (claim 4) and optionally contain fatty acids in the surfactant mixture of the six surfactants in example 2 (lines 20-21). No mention is made of the particular advantages resulting from the addition of fatty acids. The oil content of the nanoemulsion is less than 30%, whereas the oil content in our application is above 40%.

US2003/0077299a1 discloses o/w nanoemulsions comprising an ionic surfactant, an aqueous phase and an oil phase, the oil phase comprising a ceramide or a fatty acid. N-methyl-N-myristoyl taurate and sodium N-stearoyl-N-methyltaurate are two of many examples of anionic surfactants (page 1 [0016 ]]Lines 6-8). In emulsion (3) of example 1, sodium N-stearoyl-N-methyltaurate was used as an emulsifier at 2,800kg/cm²A nanoemulsion containing 16.4% silicone oil and 5% ceramide was prepared in three passes (page 4 [0060 ]) under pressure (about 40,000psi)]). The oil content is well below 40% to 75%. The absence of fatty acids reduces process energy when preparing nanoemulsions, especially when petrolatum is involved.

US20090062406A discloses aqueous surfactant concentrates consisting of isethionate, taurate and betaine surfactants, which are flowable and transparent. However, there are no nano oil droplets.

The aforementioned U.S. patent No.5,500,152 to Helliwell discloses in example 1 a shower gel containing a surfactant mixture (9% sodium cocoyl isethionate and 6% cocobetaine) and 5% silicone oil, with an average particle size of 0.4 μm (400 nm). The silicone oil was added as a pre-formed emulsion containing 50% silicone oil, 2% lauryl alcohol ethoxylate 2EO and 2% lauryl alcohol ethoxylate 21 EO. There is no mention of sodium cocoyl isethionate and fatty acid being used as emulsifiers to form a nanoemulsion to produce ethoxylate free cleaning compositions, as is the case with our application.

Ikeda et al, U.S. publication 2017/0087064(L' Oreal), relates to compositions that may be in the form of nanoemulsions or microemulsions; or it may be layered structured (paragraph 0001).

Example 4 (table 5, page 23) discloses a formulation with polyglycerol-5 oleate and polyglycerol 2-decanoate (non-ionic emulsifiers used as primary surfactants), and a small amount (0.2%) of sodium methylstearyltaurate to form a layered structure. There is no mention of the formation of oil droplets less than 300nm in size and no suggestion of the formation of nanoemulsions, as clearly indicated in examples 1 and 2, for example.

The unique nanoemulsion of the present invention contains oil droplets (400nm or less) that are aesthetically pleasing, deliver benefit agent triglyceride oils or petrolatum efficiently, and maintain excellent lather when incorporated into personal cleansing compositions. In addition, when the nanoemulsion is used in personal cleansing products, the particular surfactant used provides excellent "mild" cleansing and ensures foam retention.

Disclosure of Invention

Specifically, the present invention relates to a nanoemulsion composition comprising:

a) an internal oil phase comprising (i) from 40 to 75% by weight of the total nanoemulsion of an oil selected from the group consisting of triglyceride oils, petrolatum and mixtures thereof, wherein the petrolatum has a melting point of from 30 to 60 ℃; and (ii) 0.8-10 wt% C of the nanoemulsion₈-C₁₈Preferably C₁₀-C₁₄Fatty acids (e.g., C)₁₂Lauric acid), and

b) an external aqueous phase comprising from 1.6 to 10% by weight (as active material) of the total nanoemulsion of a sulfoalkyl ester of a fatty acid or a sulfoalkyl amide of a fatty acid, or a mixture of both;

wherein the surfactant of (b) comprises 70% or more of all surfactants present in the aqueous phase of the nanoemulsion;

wherein the volume average diameter of the oil droplets of (a) is 100-400nm,

wherein the nanoemulsion is pumpable at ambient temperature.

Preferably, the sulfoalkyl ester of a fatty acid is an alkali metal or ammonium salt of acyl isethionic acid. Preferred molecules include sodium or potassium acyl isethionate, preferably sodium acyl isethionate. Preferably, the sulfoalkyl amide of a fatty acid is an alkali metal (especially sodium or potassium) short chain (C)₁-C₃) Alkyl taurates. The preferred molecule is an alkali metal methyl alkyl taurate, with sodium methyl alkyl taurate being particularly preferred. The solubility of sodium cocoyl isethionate and sodium methyl alkyl taurate in water at 25 ℃ is only 0.01% and 1%, respectively.

Preferably, the composition of the invention comprises, in addition to the fatty acids in the oil phase, an additional surfactant solubilizer (in an amount of less than 30% of all surfactants in the aqueous phase); and preferably, the additional surfactant is an anionic or amphoteric surfactant or a mixture of both.

It is to be understood that the claims refer to compositions. That is, the claims are intended to encompass sulfoalkyl esters of fatty acids and sulfoalkyl amides of fatty acids, e.g., whether formed by us or purchased as a prepared surfactant product (as occurs in most cases).

Using fatty acids as co-emulsifiers, the nanoemulsions of the invention typically have droplets with a volume average diameter of 400 or less, or 100-; or 120-300; or 150-. Nanoemulsions based on poorly soluble surfactants (especially sodium acyl isethionate) do not solidify and are pumpable at ambient temperatures due to the use of fatty acids as co-emulsifiers.

The nanoemulsion is typically prepared by mixing the oil and water phases using a conventional rotor/stator or other type of high shear device and further processing through a homogenizer at a process pressure of 5000 pounds per square inch (psi) or less, preferably 4500psi or less. Using the same components, but without C in the oil phase₈-C₁₈Fatty acids act as co-emulsifiers and at the same pressure the droplet size will generally be much larger than when using fatty acids.

Because the sulfoalkyl esters of fatty acids (e.g., sodium acyl isethionate) and the sulfoalkyl amides of fatty acids (e.g., sodium methyl alkyl taurate) are mild cleansing surfactants and are free of sulfate and ethoxylate, the nanoemulsion composition provides a number of advantages once formed. For example, the nanoemulsion composition can be readily incorporated into a wide range of personal cleanser compositions. In addition, sodium acyl isethionate and sodium methyl alkyl taurate enable good foam formation in the detergent composition. Furthermore, the nanoemulsion of the present invention significantly improves the deposition of oil from the cleansing composition onto the skin when assisted with a cationic polymer. The nanoemulsions of the present invention provide a more affordable approach to mild and moisturizing cleansing compositions than more expensive mono-or di-carboxylic amino acid based surfactants and nanoemulsions made with these surfactants.

Thus, the novel nanoemulsions are sensorially pleasing (due to the small droplet size), provide efficient oil deposition, provide excellent stability (again due to the small droplet size), and are ideally suited for use in personal cleansing compositions, while being more cost effective.

In another aspect, the present invention relates to a method of making an emulsion comprising:

a. an internal oil phase comprising (i) from 40 to 75% by weight of the total nanoemulsion of an oil selected from the group consisting of triglyceride oils, petrolatum and mixtures thereof, wherein the petrolatum has a melting point of from 30 to 60 ℃; and (ii) 0.8-10 wt% C of the nanoemulsion₈-C₁₈Preferably C₁₀-C₁₄Fatty acids (e.g., C)₁₂Lauric acid), and

b. an external aqueous phase comprising from 1.6 to 10 wt% (as active material) of the total nanoemulsion of one or more surfactants which are sulfoalkyl esters of fatty acids such as sodium acyl isethionate or sulfoalkyl amides of fatty acids such as sodium methyl alkyl taurate, or a mixture of both;

wherein the volume average diameter of the oil droplets of (a) is 100-400nm,

wherein the nanoemulsion is pumpable at ambient temperature;

wherein the method comprises:

1) heating the aqueous phase to 55-75 deg.C;

2) heating the oil phase to 55-75 deg.C or until it melts;

3) the oil phase was added to the water phase with stirring and further mixed using a rotor/stator high shear device at 1000-,

4) pumping the coarse emulsion once through a homogenizer at a process pressure of 5000psi or less, preferably 4500psi or less; and

5) the emulsion was cooled to ambient temperature.

In step 3), alternatively, a homogenizer operating at a pressure of 200-500psi may be used to form the macroemulsion.

Detailed Description

Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". All amounts are by weight of the final composition, unless otherwise specified.

It should be noted that in specifying a range of any concentration or amount, any particular upper concentration can be associated with any particular lower concentration or amount.

For the avoidance of doubt, the word "comprising" is intended to mean "including", but not necessarily "consisting of or" consisting of. In other words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other, irrespective of whether the claims may be found without such multiple dependencies or redundancies.

The present invention provides novel nanoemulsions comprising a specific selection of oils and surfactants. The nanoemulsion can be prepared using a process pressure of 5000psi or less. The novel nanoemulsions are ideally suited for use in cleansing compositions, such as liquid cleansing compositions or soap bars.

In particular, the sulfoalkyl esters of fatty acids, such as sodium acyl isethionate, or the sulfoalkylamides of fatty acids, such as sodium methyl alkyltaurate, have a C of greater than 65%, preferably greater than 75%, preferably greater than 80%₁₄Or lower acyl or alkyl chain (preferably they have greater than 75% acyl or alkyl chain which is C₁₂，C₁₄And mixtures thereof). The emulsifiers selected provide a number of advantages when the final nanoemulsion is incorporated into a fully formulated liquid personal cleansing composition. First, isethionate and taurate surfactants are known to be less irritating than the more harsh surfactants commonly used (e.g., sodium lauryl sulfate and Sodium Lauryl Ether Sulfate (SLES) — again, as noted above, the chain length is selected to make the surfactant suitable for use in personal cleansing compositions while providing little interference with the structuring of such products.

In a co-pending application, the applicant claims similar nanoemulsions comprising N-acyl derivatives of dicarboxylic amino acids, which are more expensive and can be provided in the form of liquid solutions with 20-35% active. Small size oil droplets were obtained using fatty acids as co-emulsifiers.

In the present application, poorly soluble anionic surfactants such as sodium acyl isethionate tend to produce larger oil droplets, e.g., greater than 400nm (nm), after one pass through the homogenizer at 5000 pounds per square inch (psi) pressure when used as an emulsifier. Furthermore, nanoemulsions made with sodium acyl isethionate tend to solidify at ambient temperature and are therefore difficult to pump. Unexpectedly, we have found that the use of fatty acids as co-emulsifiers produces significantly smaller droplets and that these small droplet nanoemulsions can be obtained more efficiently. It was unexpected that the nanoemulsion of the present invention could be pumped at ambient temperature even when no solubilizer for the sodium acyl isethionate was used. However, the use of a solubilizer further enhances the pumpability of the nanoemulsion. Small droplet size and efficient processing are functions of specific combinations of specific surfactants (e.g., anions) with specific fatty acids. That is, the unique synergy between the surfactants of the present invention and fatty acids as described above works particularly well with the oils of the present invention (e.g., petrolatum).

In short, significantly smaller droplets are obtained (using fatty acids) when the same material is used, and these small droplet nanoemulsions are more efficiently obtained and can be pumped at ambient temperature. Generally, a small volume average size of the droplets helps to provide more efficient deposition. For example, cationic polymers typically used in fully formulated liquid cleaners deposit smaller droplets more readily than larger droplets. Large oil droplets also require a stabilizer to suspend the large oil droplets. The small size oil droplets from the nanoemulsion also provide greater stability when introduced into the cleaning solution. Small droplets are also considered to be more aesthetically pleasing.

The nanoemulsions of the invention are defined in more detail below.

Oil phase

The oil in the oil phase of the nanoemulsion may be one or more triglyceride oils (animal and/or vegetable oils); petrolatum; or a mixture of one or more triglyceride oils with petrolatum. Petrolatum is particularly preferred.

Examples of triglyceride oils that may be used include soybean oil, sunflower oil, coconut oil, rapeseed oil, palm kernel oil, grape seed oil, shea butter (shea butter), cocoa butter (cocoa butter) and fish oil. Soy and sunflower seed oil are preferred triglycerides.

The oil in the oil phase may also be petrolatum. The melting point of petrolatum is preferably 30 ℃ to about 60 ℃. Examples of such petrolatum include those from Unilever

Petrolatum Jelly, White PETROLATE USP from Calumet Penreco, Petrolatum G2212 and White from Sonneborn

1S。

Vegetable oils gelled with beeswax or vegetable wax are also suitable. Examples of such gelled vegetable Oils include NaturalAtum from Koster Keunen, Inc. and Unputroleum Jelly from Camden-Grey Essential Oils, Inc.

The range of oil is 40 wt% to 75 wt%, preferably 41 wt% to 65 wt% of the total nanoemulsion composition. The preferred volume average diameter of the triglyceride oil or petrolatum droplets is 100-400nm, preferably 120-350nm, more preferably 150-300 nm.

When triglyceride oils and/or petrolatum are deposited on the skin after washing the skin with a fully formulated cleansing composition having the nanoemulsion of the present invention incorporated therein, the choice of triglyceride oils and petrolatum helps to impart emolliency and occlusive properties to the skin.

In addition to the triglyceride oil(s) and/or petrolatum, the oil phase may comprise oil-soluble skin benefit actives such as vitamin a, vitamin E, sunscreens, fragrances, retinol palmitate, 12-hydroxystearic acid, conjugated linoleic acid; an antibacterial agent; mosquito repellent, and the like.

Another ingredient that may be found in the oil phase is an oil phase stabilizer. For example, small amounts (0.01 to 2%, preferably 0.1 to 1% by weight of the nanoemulsion) of antioxidants may be used. When the oil used is a triglyceride, a preferred antioxidant that can be used is Butylated Hydroxytoluene (BHT). This is typically used as a food grade antioxidant.

Besides oil, the oil phase contains C₈To C₁₈Preferably C₁₀To C₁₄Fatty acids in an amount of 0.8-10 wt.%, preferably 1-7 wt.%, of the total nanoemulsion. Examples of fatty acids that may be used include lauric acid, myristic acid, palmitic acid, stearic acid, coconut oil fatty acid, and mixtures thereof. Lauric acid is preferably used as a co-emulsifier. For example, the oil phase may comprise 40-70% by weight, preferably 41-65% by weight of the nanoemulsion of petrolatum and 0.9-8% by weight of the nanoemulsion of lauric acid.

Aqueous phase

The aqueous phase contains a poorly water soluble anionic surfactant, sodium acyl isethionate or sodium methyl alkyl taurate or both. These surfactants have a solubility of 0.01 to 1% at ambient temperature. These surfactants have a C of greater than 65%, preferably greater than 75%, preferably greater than 80%₁₄Or lower acyl or alkyl chain (preferably they have greater than 75% acyl or alkyl chain which is C₁₂，C₁₄Or mixtures thereof). Preferred acyl isethionates are cocoyl or lauroyl isethionates and preferred taurates are cocoyl or lauroyl taurates. These are predominantly short-chain acyl groups (e.g. relative to longer-chain C)₁₆And C₁₈) Ensuring that when the nanoemulsions of the present invention are incorporated into fully formulated cleaning compositions (e.g., liquid cleaning compositions), they help maintain or enhance foaming capacity.

The acyl isethionate surfactant component is typically prepared by reacting isethionate with fatty acids having 8 to 20 carbon atoms and an iodine value (a measure of unsaturation) of less than 20, for example:

HOR¹SO₃M+RCOOH→RCOOR¹SO₃M

wherein R is¹Is an aliphatic hydrocarbon group having 2 to 4 carbons;

m is an alkali metal cation (e.g., sodium, potassium), ammonium or substituted ammonium cation or other counterion; and

r is an aliphatic hydrocarbon group having 7 to 21, preferably 9 to 17 carbons.

Depending on the process conditions used, the fatty acyl isethionate product obtained may beAs a mixture of 40-85 wt.% fatty acyl isethionate (which is formed by the reaction) and 50 to about 12 wt.%, typically 40-20 wt.%, free fatty acid. In addition, the product may contain isethionate, which is typically present in an amount less than 5 wt.%, and trace amounts (less than 2 wt.%) of other impurities. The acyl chain length distribution of fatty acyl isethionates is controlled by the chain length distribution of the fatty acids. Preferably, mixtures of fatty acids are used to prepare commercial acyl isethionate surfactants. Typically, coconut fatty acids are used, which are rich in lauric acid, yielding cocoyl isethionate. By mixed distillation of different fractions of fatty acids to enrich certain chain lengths, e.g. C, in the final reaction product₁₂The chain length distribution can be further adjusted. The resulting acyl isethionate surfactant (e.g., resulting from the reaction of alkali metal isethionate and aliphatic fatty acid) should have greater than 65 wt.%, preferably greater than 75% (based on acyl isethionate reaction product) of acyl groups having 14 or fewer carbon atoms to provide both lather and mildness of the resulting acyl isethionate product. The resulting acyl isethionate surfactant and unreacted fatty acid typically form poorly soluble surfactant/fatty acid crystals in water at ambient temperature.

An example of a commercial acyl isethionate product particularly useful in the present invention is DEFI flake, produced by Union Rivas

Major components in soap bars. DEFI (direct esterification of fatty isethionate) flakes typically contain about 68-85 wt.% fatty acyl sodium isethionate and 12-30 wt.% free fatty acid. Greater than 65%, preferably greater than 75% by weight of the acyl groups of the resulting acyl isethionate have 14 or fewer carbon atoms. The acyl isethionate surfactant product is extremely mild to the skin and has very good lather.

Other suppliers of acyl isethionates include Huang Yonggan (e.g., YA-SCI-65 and YA-SCI-85), Innospec (e.g., Pureac SLI), Clariant (e.g., Pureact SLI)SCI-85P)。

Sodium methyl alkyl taurate is structurally and synthetically closely related to acyl isethionates. The precursor N-methyl taurine of sodium methyl alkyl taurate can be economically prepared from sodium isethionate:

H₂NCH₃+HOCH₂CH₂SO₃M→HN(CH₃)CH₂CH₂SO₃Na⁺H₂O

where M is an alkali metal cation (e.g., sodium, potassium), ammonium or substituted ammonium or other counterion.

For example, N-methyl taurine is further reacted with fatty acids to produce sodium methyl alkyl taurate:

HN(CH₃)CH₂CH₂SO₃Na+RCOOH→RCON(CH₃)CH₂CH₂SO₃Na

r is an aliphatic hydrocarbon group having 7 to 21, preferably 9 to 17 carbons.

As with acyl isethionates, the resulting alkyl taurate product, such as sodium methyl alkyl taurate, may be a mixture of sodium methyl alkyl taurate, free fatty acids and other residues. The chain length distribution of the fatty acids is used to determine the chain length distribution of the alkyl taurates. Coconut fatty acids, which are rich in lauric acid, are commonly used, resulting in cocoyl taurates. The chain length distribution can be further adjusted by co-distilling different fractions of fatty acids to enrich certain chain lengths, e.g., 12 carbons, in the final reaction product. The resulting fatty alkyl taurate surfactant should have greater than 65 wt.%, preferably greater than 75% (based on the alkyl taurate reaction product) of fatty acyl groups having 14 or fewer carbon atoms to provide both lather and mildness to the resulting fatty alkyl taurate product. The solubility of sodium methyl cocoyl taurate in water at 25 ℃ is about 1% by weight. It may be provided as a paste with 20-35% active material, for example Pureact WSConc by Innospec, which is 30% active material. Other supplier bagsIncluding Galaxy (e.g., Galsoft SLT), Solvay Novecare (R) ((R))

TC-42LQ), Croda (Adinol CT95) and Clariant (Hostapon CT paste)

When a petrolatum nanoemulsion was prepared using a homogenizer at 5000psi using sodium cocoyl isethionate and sodium methylcocoyl taurate as the only emulsifiers, both produced oil droplets well above 400 nm; furthermore, sodium cocoyl isethionate based emulsions solidify on storage at ambient temperature, making them non-pumpable. This is due to the limited solubility of sodium acyl isethionate in water, which leads to crystallization in the aqueous phase of the emulsion and renders the emulsion non-pumpable. A conventional approach to addressing the pumpability problem is to use a solubilizer for sodium cocoyl isethionate in the aqueous phase to aid in its dissolution. Such solubilizers are ionic surfactants consisting of head groups similar to or larger and more complex than those of sodium acyl isethionate. Both anionic and amphoteric surfactants can achieve this. The main unexpected finding of the present invention is that the use of fatty acids as co-emulsifiers instead of using solubilizers not only prevents the solidification of the emulsion based on sodium acyl isethionate and thus allows pumping, but also significantly reduces the oil droplet size to half or one third of that when no fatty acids are used. The addition of fatty acids, in particular lauric acid, as co-emulsifier results in the formation of pumpable nanoemulsions and the efficient formation of smaller oil droplets to form highly excellent nanoemulsions. For example, it is possible to produce petrolatum droplets of about 200nm in size by passing through the homogenizer only once at 5000psi (see example 1).

In addition, other mild ionic cleansing surfactants that may also be used as solubilizers may be used in the aqueous phase. Anionic surfactants that may be used include amino acid based surfactants such as acyl glutamates, acyl aspartates, acyl glycinates, acyl alanates and acyl sarcosinates. Amphoteric surfactants such as cocobetaine, cocamidopropyl betaine, sodium lauroamphoacetate, lauramidopropyl hydroxysultaine and cocamidopropyl hydroxysultaine may also be used and are preferred. These co-surfactants are typically present in the aqueous phase in an amount of less than 30% of the total surfactant. Nonionic surfactants should preferably be avoided in the aqueous phase, since those surfactants generally produce poor foaming.

The total surfactant in the aqueous phase comprises 1.6-10 wt%, preferably 4-8 wt% of the total nanoemulsion. As noted, poorly soluble sodium acyl isethionate, or sodium methyl acyl taurate, or mixtures thereof, are the primary surfactants for the nanoemulsion. They constitute 70% or more, preferably 80% or more of all surfactants in the aqueous phase. They may of course be the only surfactants present in the aqueous phase.

Preferably, the aqueous phase may comprise one or more preservatives. In general, they are present in a content of from 0.01 to 1.0% by weight, preferably from 0.1 to 0.5% by weight.

Additionally, a polyol may be included in the aqueous phase. Examples of polyhydric alcohols are glycerol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1, 3-butylene glycol, 1,2, 6-hexanetriol, ethoxylated glycerol, propoxylated glycerol or mixtures thereof. When water soluble alkali metal (e.g. potassium) or ammonium salts of acyl isethionic and/or alkyltaurines are used as the primary anionic emulsifier, the polyol content in the aqueous phase can be significantly high, resulting in a weight ratio of polyol to water of from 1:3 to 3: 1. This ratio can increase the efficiency of production of the nanoemulsion, thereby eliminating the need for high pressure homogenization. When sodium salts of acyl isethionic acid and/or alkyl taurines are used as the primary anionic emulsifier, little or no polyol (e.g., 0-5 wt%, preferably 3 wt% or less, or 2 wt% or less) should be included in the aqueous phase due to their poor solubility in water.

The nanoemulsions of the invention have a volume average diameter (also used interchangeably with the terms "volume average diameter" or "volume average size") of 400nm or less, preferably 100-350nm, more preferably 120-300 nm.

Nanoemulsions having droplet sizes in these ranges are obtained in the present invention using a high pressure homogenizer or a high pressure sonic generator (sonolator). The pressure used is 5000psi or less, preferably 4500psi or less.

Preparation of the nanoemulsion

The nanoemulsion is typically formed in a two-stage process.

The first stage is used to form a coarse emulsion. Heating the oil phase and the aqueous phase to 75 deg.C (55 deg.C-75 deg.C) respectively to make each phase clear and uniform (heating the oil phase to 55-75 deg.C or melting); the oil phase was then mixed with the water phase with vigorous mixing. Intensive mixing can be accomplished by conventional means, including mixing the materials in a stirred tank, and then passing the mixture through a rotor/stator mixer (e.g., a rotary/stator mixer)

High shear in-line mixers), or in a vessel with a high shear mixer (e.g., in-line mixers)A Turbon mixer) mixes them. Alternatively, the macroemulsion may be produced by using a continuous high shear mixing device, such as a standard Sonic generator device produced by Sonic Corporation of Connecticut. These standard sonic generators are typically operated at pressures of 200-500psi to form the crude emulsion.

The second stage of the process is to pass the crude emulsion through a high pressure homogenizer to form a nanoemulsion. The high pressure homogenizer used in the present invention is the Nano DeBee homogenizer from BEE International (Mass.) and a high pressure acoustic wave generator unit also manufactured by Sonic Corporation, Connecticut, U.S.A. These devices can be operated at pressures up to 1000-. Other suppliers of homogenizers may be used as long as they can operate at pressures up to 1000-. For hydrophobic oils that are petrolatum or triglycerides, the desired nanoemulsion particle size can be achieved by passing the Nano DeBEE or high pressure sonic generator only once when the fatty acid is included as a co-emulsifier.

In the examples, the following terms are defined as follows:

d [4,3 ]: volume mean diameter or volume mean size

The volume mean diameter is determined by a Malvern Mastersizer.

Examples

Examples 1-4 and comparative example A:

the macroemulsion was prepared in a one liter ESCO mixer equipped with a rotor/stator high shear device (ESCO-LABORAG, Switzerland). The aqueous phase was added to the ESCO mixer and heated to 75 ℃ or until clear. The oil phases were combined and heated to 75 ℃ or until melted in a separate vessel. The oil phase is gradually added to the aqueous phase in the ESCO mixer with stirring and/or intensively mixed by a rotor/stator device. When all oil phase addition was complete and the macroemulsion was formed in the ESCO mixer, the macroemulsion was transferred and passed through the high pressure homogenizer Nano DeBEE once at 5000psi process pressure to reach the desired droplet size.

YA-SCI-85 containing 84% sodium cocoyl isethionate, 12% fatty acid and 4% sodium isethionate

Required amount (e.g. to obtain 100 wt%)

In comparative example a, sodium cocoyl isethionate was the only emulsifier for making the petrolatum nanoemulsion. The oil droplet size was 425nm, above 400 nm. Most undesirable is that the resulting emulsion solidifies into the shape of its container upon storage at ambient temperature due to the limited solubility of sodium cocoyl isethionate. The emulsion prepared in comparative example a was not pumpable at ambient temperature due to its solid nature. In example 1, when 3.5% fatty acid (not a solubilizer for sodium cocoyl isethionate) was used as a co-emulsifier, the oil droplet size was reduced by half to 215nm, and most unexpectedly, the resulting nanoemulsion had a skin cream-like consistency and could be easily pumped at ambient temperature after storage. In examples 2-4, both a fatty acid and a solubilizer for sodium cocoyl isethionate (such as sodium lauroamphoacetate and sodium methylcocoyltaurate) were incorporated into the emulsion formulation, the resulting nanoemulsion ranged in droplet size from 191-234nm, and the lotion-like emulsion could be easily pumped at ambient temperature after storage.

Examples 5 to 6 and comparative examples B to C

Examples 5-6 and comparative example B were prepared in analogy to examples 1-4 and comparative example A.

Required amount (e.g. to obtain 100 wt%)

In comparative example B, sodium methyl cocoyl taurate was provided as a 20% dispersion. The dispersion is a white paste due to its low solubility. When used as the sole emulsifier, the resulting emulsion produced by homogenization at 5000psi produced oil droplets of 600nm, even greater than the oil droplets of comparative example a using sodium cocoyl isethionate, although the former were pumpable and the latter were non-pumpable, possibly due to their different solubilities in water at ambient temperature. In example 5, using fatty acids as co-emulsifiers, the oil droplet size was reduced by more than half to 262nm in the resulting nanoemulsion.

Examples 7 to 10: the nanoemulsion was formed using 60% petrolatum, with sodium cocoyl isethionate (YA-SCI-85) as the primary emulsifier in the aqueous phase and lauric acid as the co-emulsifier in the oil phase. The macroemulsion was prepared in a 450 lb stirred jacketed kettle equipped with an eccentric turbine, a scraper and a recirculation loop along which a pump and a Silverson on-line rotor/stator double screen mixer (model 150/250 MS) were fixed. The aqueous phase was added to the kettle and heated to 75 deg.C, while the oil phase was heated to 75 deg.C in a separate kettle. The oil phase was then charged to the water phase through a recirculation loop, and an in-line rotor/stator dual screen mixer was operated at 6000rpm while a pump was pumping the water phase through the recirculation loop. After the oil phase addition was complete, the mixture in the stirred tank was pumped through the recirculation loop 3 theoretical passes (the volume of mixture in the tank divided by the flow rate in the recirculation loop), and the rotor/stator twin-sieve mixer was run at 6000 rpm. The crude emulsion is then pumped only once through a high pressure sonic generator at pressures up to 2500psi to form the nanoemulsion.

Required amount (e.g. to obtain 100 wt%)

Claims

1. A nanoemulsion composition, comprising:

a) an inner phase comprising:

(i) 40-75% by weight of the total nanoemulsion composition of an oil selected from the group consisting of triglycerides, petrolatum and mixtures thereof, wherein the petrolatum has a melting point between 30-60 ℃; and

(ii) 0.8-10% by weight of the nanoemulsion of C₈-C₁₈A fatty acid; and

b) an external aqueous phase comprising from 1.6 to 15 wt% (as active) of the total nanoemulsion composition of one or more surfactants which are alkali metal or ammonium salts of isethionic acid; alkali metal C₁-C₃Alkyl taurates; or a mixture of the two,

wherein the alkali metal salt or ammonium salt of isethionic acid; alkali metal C₁-C₃Alkyl taurates; or a mixture of both, comprises 70% or more of all surfactants present in the external aqueous phase of the nanoemulsion;

wherein the volume average diameter of the droplets of the inner phase is 100-400 nm.

2. The nanoemulsion of claim 1, wherein the alkali metal or ammonium salt of isethionic acid is sodium acyl isethionic acid.

3. The nanoemulsion of claim 1 or 2, wherein the alkali metal C₁-C₃The alkyl taurate is sodium methyl alkyl taurate.

4. The composition according to any one of claims 1-3, wherein the volume average diameter is 120-300 nm.

5. The composition according to any one of claims 1-4, further comprising a surfactant in the aqueous phase, the surfactant selected from the group consisting of cocobetaine, cocamidopropyl betaine, lauroamphoacetate, hydroxysultaine, and mixtures thereof.

6. The composition of claim 5, wherein the additional surfactant comprises up to 30 wt% of the aqueous phase surfactant.

7. The nanoemulsion composition of any of claims 1-6, wherein the oil is a triglyceride oil, and the triglyceride oil is selected from the group consisting of soybean oil, sunflower oil, coconut oil, rapeseed oil, palm kernel oil, grape seed oil, fish oil, and mixtures thereof.

8. The nanoemulsion composition of any of claims 1-6, wherein the oil is petrolatum, and the petrolatum has a melting point between 30-60 ℃.

9. The nanoemulsion composition of any of claims 1-6, wherein the oil is an oil mixture comprising triglyceride oil and petrolatum.

10. The nanoemulsion composition of any of claims 1-9, wherein the polymer has a chain length C₈-C₁₈The fatty acid of (a) is selected from lauric acid, myristic acid, coconut oil fatty acid and mixtures thereof.

11. The nanoemulsion composition of claim 10, wherein the fatty acid is present at a level of 1-7%, by weight of the nanoemulsion.

12. The nanoemulsion composition of any of claims 1-11, wherein the nanoemulsion was prepared under pressure from a homogenizer or sonic generator, and the pressure was 5000psi or less.

13. A method of making an emulsion comprising:

a) an inner phase comprising:

(ii) 0.8-10% by weight of the nanoemulsion of C₈-C₁₈A fatty acid; and

wherein the alkali metal salt or ammonium salt of isethionic acid; alkali metal C₁-C₃Alkyl taurates; sulfoalkyl esters or amides of fatty acids; or a mixture of both, of 70% or more, preferably 75-100% of all surfactants present in the external aqueous phase of the nanoemulsion;

wherein the volume average diameter of the oil droplets of the inner phase is 100-400 nm;

wherein the method comprises:

1) heating the aqueous phase to 55-75 deg.C;

2) heating the oil phase to 55-75 deg.C or until it melts;

3) the oil phase was added to the water phase and mixed using a rotor/stator high shear device at 1000-,

4) pumping the coarse emulsion through a homogenizer once at a process pressure of 5000psi or less; and

5) the emulsion was cooled to ambient temperature.

14. The method as claimed in claim 13, wherein in step 3) the macroemulsion is formed using a homogenizer operated at a pressure of 200-500psi instead.